The present invention relates to an electronic device incorporating a system power supply unit and a method for generating and supplying power supply voltage.
A highly integrated semiconductor integrated circuit device (LSI) and an electronic system such as an electronic device is formed by a plurality of circuits and a plurality of devices having specific functions. An electronic system incorporates a system power supply unit for supplying power to each of a plurality of loads such as circuits and devices (refer to Japanese Laid-Open Patent Publication No. 2000-228833). The power supply voltages that are to be supplied to the loads may differ depending on the time or technology under which the loads were formed. Accordingly, there is a demand for a system power supply unit that generates a plurality of voltages corresponding to the loads and supplies each load with the appropriate voltage.
A system power supply unit in the prior art includes a plurality of DC-DC converters. Each DC-DC converter is set to generate voltage supplied to each circuit or device and output voltage that is controlled to be constant.